We supplied concrete for a wastewater treatment plant for which the specifications required an entrained air content of 6% ± 1%. An elevated exterior walkway required 12 cubic yards which were delivered in two loads. The testing laboratory inspector performed an air test on the first load and told our driver and one of the contractor's workers that the air content was 3%, which was too low. A test on the second load also indicated a 3% air content, but the inspector didn't reject either load. About two hours later, the contractor called and told me the concrete had to be torn out because of the low air content and that we had to pay the entire cost of removal and replacement. We believe the contractor and testing laboratory should pay for this since they both knew the air content was out of spec but did nothing to stop the pour or reject the loads. The contractor didn't inform us during the pour that the air content was low, but since then a petrographic analysis has confirmed the low air content. How should we argue this case? And do you know of a sealer that could protect this concrete?
Let's talk about the concrete acceptance first. Even though the inspector told your driver that the air content was low, your driver doesn't have the authority to reject a load of concrete. Depending on the contract documents, the inspector also may not have the authority to reject a load of concrete. Find out who had the authority to reject concrete at the jobsite. If it's the contractor, and he placed the concrete, he accepted the concrete by placing it. You could argue that he owns the concrete. You don't say where you're located. We assume it's a cold climate and that freeze-thaw cycles are a concern. However, if the concrete won't be subjected to deicing salts, a 3% air content may allow it to weather the freeze-thaw cycles without damage. When air-entrained concrete was first introduced, a common requirement for providing freeze-thaw resistance was an air content of 3% to 5%. Later, as more and more salt was used, increasing air contents were specified to improve resistance to the salts. If there aren't any salts, 3% may provide adequate durability. Did the petrographic report indicate whether the air content was 3% or more? A sealer may help, but isn't guaranteed to protect non-air-entrained concrete. You could try offering to apply one of the many sealers on the market and give a five-year guarantee that you will replace the walkways if they deteriorate.